In rail vehicle braking systems it has become established practice to employ air under pressure in a brake pipe running the length of a train as the control means whereby brakes are applied and released. More specifically, it has been preferable to establish a system pressure, a decrease in which pressure in the brake pipe gives rise to a brake application, and a subsequent recovery of which permits the release of the brakes.
The use of air under pressure for control of the brakes in the above manner has certain shortcomings in a long train because not only can the rate of propagation of a pressure signal be no greater than the speed of sound but more significantly, where the system relies upon a reduction of brake pipe pressure by passing air from one end of the train to another through the brake pipe, the resistance to such flow of air through the brake pipe can introduce substantial delays between the operation of the brakes on spaced vehicles of the train. The present invention seeks to advantageously reduce the above more significant shortcoming.
According to the present invention there is provided in a rail vehicle braking system an arrangement for improving brake signal propagation in a brake pipe, the arrangement including a valve and a fluid flow sensor connected into a section of a brake pipe and to be responsive to flow rate in the brake pipe, said valve being responsive to the flow sensor to effect enhancement of a brake pipe pressure change produced by flow therein. The arrangement preferably is constructed so as to effect the enhancement only upon the occurrence of a predetermined pressure change to be propagated in the pipe, so as to render the arrangement non-responsive to pressure changes of other than a predetermined sense and to steady pressure gradients and flow as might be caused by a leak in the system, thus responding only to predetermined changing pressures in the brake pipe.
In a braking system, one or more said arrangements may be included at the points based along the brake pipe of a train from a brake pipe control valve and thereby reduce delays in response of the brakes along the train.